Combining methods to conduct a systematic review and propose a conceptual and theoretical framework in socio-environmental research

Highlights • SODIP steps provide robustness and efficiency for theoretical/conceptual framework.• Systematic review articles combined with georeferenced data support the framework.• Combination of scientific and policy data supports theoretical/conceptual framework.• Using open-source tools is essential for better evaluation and visualization of data.


SODIP step 1: systematic review and meta-analysis
Defining the systematic review study Basic steps of planning to conduct a review study are necessary.Guiding questions must be answered, mainly to identify the topic addressed and define the proposed theoretical framework ( Table 1 ).To define the questions, the cognitive map [6] (Siau and Tan, 2005) can be used, as it facilitates the process of identifying the problem and its questions that will help to design the research protocol ( Fig. 1 ).The protocol must be elaborated, database searches conducted, articles screened, extraction and critical analysis of data performed, data synthesized, the report created and finalized review performed [7] .The definition of a review protocol is an extremely relevant step, as it promotes coherence, integrity and transparency in this type of study [8] .
An important step in review studies is the definition of objectives, which must be qualitatively (data visualization) or quantitatively (statistical analysis) measurable ( Table 2 ).The objectives define the direction that the systematic review will take, whether it is a critical analysis of published research, addresses methodologies used for a given topic or an exploratory assessment to present research evidence.
Once the questions (issue) and objectives of the review study have been defined, it is necessary to define the timeline or time scale of the study to be used to elaborate the protocol.

Protocol search
The protocol describes the methodology used step-by-step to conduct review studies.Para elaborar o protocol é necessário definir o contexto do estudo de revisão, desde a escala temporal, a delimitação espacial, palavras-chave, os critérios de inclusão e exclusão e as bases de dados a serem consultadas.The definition of topics was based on the Protocol Search Appraisal Synthesis Analysis

Question for systematic review and theoretical framework Objective
What is the theory of the topic to be studied?Identify the main theme What are the variables of interest?
Identify the variables of interest Fill in the gaps What are the main gaps in knowledge?
Identify the main challenges in the topic addressed What are the main challenges of this topic?
Define the main topics covered What are the trends in studies on this topic?
Identify the main trends and gaps to define the framework

Table 2
Examples of objectives in review studies.

Title Objective
Beyond PRISMA: Systematic reviews to inform marine science and policy "We identified eighteen systematic reviews published on marine topics between 2008 and 2015 ″ [10] A review of remote sensing for mangrove forests: 1956-2018 "The objectives of this study are: 1) to identify key milestones of RS of mangrove forests to provide a historical overview of this research field in the chronological order; 2) to discover key drivers for the evolution of different milestones to analyze theoretical developments of mangrove RS, and 3) to project future research directions in mangrove RS. " [11] Review of valuation methods for mangrove ecosystem services "We present a comprehensive overview and summary of studies undertaken to investigate the ecosystem services of mangrove forests.We address the variety of different methods applied for different ecosystem services evaluation of mangrove forests, as well as the methods and techniques employed for data analyses, and further discuss their potential and limitations."[12] The costs and benefits of REDD + : A review of the literature "We conducted a review of 60 unique REDD + costs and benefits studies." [13] Systematic Review of Spatial Planning and Marine Protected Areas: A Brazilian Perspective "This article offers a systematic review through a comparative meta-analysis of the literature on MPAs and spatial planning.Specific goals of this study are (I) to identify studies on Brazil; and (II) to compare and contrast these with studies performed elsewhere." [14] Analyzing 70 years of research output on South African estuaries using bibliometric indicators "This study examined scientific papers published in authoritative international journals authored by researchers working on South African estuaries between 1949 and 2020 ″ [15] Brazilian Mangroves: Blue Carbon Hotspots of National and Global Relevance to Natural Climate Solutions "We provide a direct comparison between mangroves and Brazil's other major vegetated biomes, identifying mangroves as a major carbon hotspot that can help meet Intended Nationally Determined Contributions (NDCs), in addition to their significance as global coastal carbon sinks."[16] Integrating a conceptual framework for the sustainable development goals in the mangrove ecosystem: A systematic review "The present study aimed to propose a conceptual framework for SDG in relation to the mangrove ecosystem, as a baseline scenario, based on a systematic review relating them to Ramsar Sites." [4] Report (PSALSAR) ( Table 3 ) and Population Intervention, Comparison, and Outcomes (PICOC) framework ( Table 4 ) [5] in order to identifying evidence needs.
The essential steps of the protocol in review studies are: (i) selection of temporal scale; (ii) selection of spatial scale; (iii) selection of search words; (iv) selection of search operators; (v) selection of search sections; (vi) selection of databases for scientific documents; and (vii) inclusion and exclusion criteria.
i. Selection of temporal scale through the search dates are an important point.An important point to be raised and which is not common in review studies is the identification of international events and treaties according to the topic covered.This can be used as a baseline to define the time scale.In the same time, the database or criteria defined by the researcher based on a relevant factor such as an international treaty (e.g., Ramsar Convention) or important date (e.g., the definition of the 2030 Agenda and the SDGs) ( Table 5 ).ii.Selection of spatial scale or multiple scales ( Fig. 2) is related to the type of review study being conducted: (i) Global, (ii) Transnational, both appropriate for Earth System Science, International Law, and International Relations, (iii) National, (iv) Regional, both appropriate for global sustainability science (law, sociology, political science, geography, and development studies), (v) Community, and (vi) Individual [20] .iii.The selection of search words must be carefully chosen, in two ways depending on the spatial scale of the review study as this will define the type of analysis.To obtain greater precision in the search, the words must be combined [18] .Abbreviations can be used, as long as they are found in the literature (e.g., SDG OR SDGs referring to Sustainable Development Goals) or even compound words (e.g., Land use OR Land-use).Some encodings must be used for the search to be more accurate and efficient ( Table 6 ).In this step, PRISMA is often used, although this reporting methodology is used in the screening of the data, it is also a reference to carry out more accurately [8] .

Table 4
PICO framework of the systematic review studies.iv.Selection of databases for scientific documents: The selection of databases must be chosen carefully ( Table 6 ).Some articles present evidence and discrepancies between the databases for commonly used review studies, especially regarding their efficiency [19 , 21-23 ].Some of the most common databases are: (i) Web of Science (WoS), (ii) Scopus, (iii) Scielo, and (iv) Google Scholar.v. Selection of search operators: In this step, the Boolean operators are selected and everything will depend on the scope of the studies that will be selected in the review study ( Table 7 ).vi.Selection of search sections: Search sections refer to sections in the document (e.g., title, abstract, keywords) and other components (e.g., funding, author).Although there is a wide range of sections to choose from, "Title ", "Abstract " and "Keywords " are the most efficient [24] (see "carbon sequestration, " "carbon accumulation, " "wood production, " "biomass production, " "stem growth, " "basal area increment, " and "DBH increment" are always in combination with the terms "mangrove" and "Brazil."Portuguese terms "carbono" (for carbon) and "mangue * " (for mangrove or mangal) Google Scholar, Science Direct, Web of Science, and the Brazilian SciELO vii.The inclusion and exclusion criteria support selecting documents and improving the filtering of them.Therefore, it is extremely important to define them in accordance with the previous steps ( Table 10 ).viii.Selection of databases for other types of information: Selection of other databases will depend on the purpose of the review study, whether it will include data on ecology, spatial issues, legislation documents, historical data, etc.Although there are few databases on global policies, it is important to include legislation documents and unify them with scientific data [25] .In Table 9 presents some databases on socio-environmental issues.

Review reporting
PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) is a report that helps to document the a priori route of the systematic review [8] .The review reporting consists of two stages [28] : (i) the procedure using the PRIS report and (ii) the description of the results from the applied presentation MA.To perform this report, there are predefined spreadsheets in the following formats:

Table 10
Inclusion and exclusion criteria.

Spatial scale
Review studies with location or spatial scale criteria.
• Studies in the mangroves of South America • Studies around the world • Studies in a particular country Temporal scale If the study is intended to compare before to after an important date.
• Studies from the Ramsar Convention (1971) • Studies after the declaration of the 2030 Agenda and the SDGs (2015) Section Sections such as title, abstract and Keywords can be criteria for the most efficient search.
• Scientific documents in Title search only (see the difference in Table 7 ) Language This criterion will depend on the spatial scale of the studies and also defines the local databases.
• Local studies must follow searches in the language of the country combined with English: Brazil -Portuguese, Peru -Spanish.

• Local studies with local databases: Systematic Review of Spatial
Planning and Marine Protected Areas: A Brazilian Perspective [14] .

Type of document
There are several types of documents in the databases; their selection is a relevant criterion to take into account.
• Scientific articles to systematize methodologies and case studies

Table 11
List of software for statistical analysis.

Software
Description Site

Kappa coefficient (Kw) for validation
The Cohen's kappa coefficient (Kw) statistic is used to calculate the level of agreement of selected documents between reviewers [7] .This statistical test is based on an agreement matrix [30 , 31] .Validation using the Kappa weighting method is a way of providing reliability to review studies [32] .To carry out the selection of documents, manually, through Kw, authors must define the main criteria for selection.For example: (i) studies that directly mention the search words in the title, (ii) studies that use innovative methodologies, (iii) studies that are within the spatial scale of the scope of the systematic review study.After that, the agreement matrix is built according to the format required by the software that will be used (see example in Table 12 ).

Appraisal
At the end of the systematic review of documents and data, an evaluation must be carried out to monitor the results obtained [7] .In this sense, guiding questions can be asked: • Were the search words sufficient to obtain documents that answer the question and objectives?
• Was the spatial and temporal scale sufficient to answer the question?
• Were the documents or data from secondary sources obtained sufficient to answer the question?
• Were the inclusion and exclusion criteria sufficient to obtain the necessary documents?

SODIP step 2: open-source (software and data) use
The open-source means that the source of the software or data can be modified by an interest group for the purpose of contribution, in addition to being freely accessible to a source of data or software available [33] .Therefore, the use of open-source software is essential, especially due to the reduction or non-existence of costs to manage the data collected in the systematic review.

Statistical analysis and data visualization
The choice of type of statistical analysis depends on the spatial scale of the systematic review study ( Fig. 2 ).For example, studies that try to identify the trend in a specific ecosystem globally (e.g."mangrove * ") or locally ( "spatial plan * " AND "Brazil ") will use more powerful statistical tools such as machine learning or Geographic Information System (GIS).If the studies are intended to evaluate more specific topics, the analysis will be based on descriptive statistics ( Table 11 ).See Table 9 for choose database.

SODIP step 3: data visualization and design information
Data visualization is not a simple process, but we can use design and science outreach tools.Therefore, it is essential to direct the visualization and design of systematized data according to the target audience to work as a bridge between society and science [52] .When we manage large amounts of data obtained, for example, from the Scopus or WoS databases, we can facilitate the funneling process by adding systematic review pipelines as a promising tool for optimizing and speeding up the performance of systematic reviews.In addition, Artificial Intelligence (AI) and Machine Learning (ML) have enabled the development of Artificial Intelligenceaided pipelines that assist in finding relevant texts for search tasks.

Data pipeline with ASReview
In addition to being freely accessible, this software has a robust potential for document selection by machine learning [36] .The phases for the selection of documents through this tool are: (i) pre-screening selects the documents, (ii) screening to evaluate the documents by relevance and (iii) post-screening to evaluate the relevance according to the training of the statistician [36] .For example, in one study, more than 10,000 documents were found that were filtered through this tool, excluding 95 % of the documents, leaving for analysis more than 200 documents directly related to the topic addressed [53] .This tool uses Naive Bayes, among other types of statistical analysis, where it is possible to obtain the selected documents (example Fig. 3 ).

Visualization of temporal and spatial data
The information obtained can be translated into figures that show the spatial scale (e.g., maps with georeferenced data) and the temporal scale (e.g., serial figures).For spatial data, a heat map (Kernel map) created by using QGis can be used ( Fig. 4 ), while temporal data can be presented through a timeline ( Figs. 5 and 6 ).Data can be visualized using design such as RawGraphs without needing to know programming language ( Fig. 7 ).The information must have a statistical basis and for this, qualitative analysis tools such as Voyant, for creating a word cloud, or Iramuteq, for similarity analysis ( Fig. 8 ), Reinert Method clusters ( Fig. 9 ), and Correspondence Factor Analysis ( Fig. 10 ).Table 11 presents more open-source tools.

Collaborative information libraries
Review studies generate a dataset and can be made available in collaborative libraries through open-source tools such as Mendeley and Zotero [54 , 55] .Likewise, funneled data can be made available through repositories such as Mendeley Data, as it can be the basis for preparing other articles [56] .See the example of a collaborative library about mangroves that has been developed ( https://tinyurl.com/mangrovecollaborative ).

SODIP step 4: identifying gaps, challenges and trends
In most reviews we find qualitative data that needs to be analyzed, for example, the sections of articles selected from the Scopus and WoS databases.Sections such as the title, keywords and summary offer information necessary to carry out a theoretical analysis and a scientific diagnosis of the main topics covered in a given type of study.At the same time, there are many qualitative data    analysis tools, most of which are paid software, such as NVivo and MAXQDA.Iramuteq, in addition to being free access software, is a very powerful tool for qualitative analysis, serving as support for identifying gaps, challenges, and trends.

Iramuteq
This software is based on the R language and can be used to visualize and analyze qualitative data through several analyses: (i) word cloud that group and organize words based on their frequency [57] ( Fig. 11 ), (ii) similarity analysis ( Fig. 8 ), ( iii ) cluster Reinert Method ( Fig. 9 ), (iv) Prototypical analysis and (v) Correspondence Factor Analysis ( Fig. 10 ).The word cloud is supported to identify the most frequently studied topics in the documents, from this automated identification we can define topics for the review study.See more examples of the Similarity Analysis and Descending Hierarchical Analysis (DHA) in the article "Systematic Review of Spatial Planning and Marine Protected Areas: A Brazilian Perspective " [14] .Similarly, this tool can help in the document content analysis

Table 13
Examples of studies on conceptual and theoretical frameworks.process through the co-occurrence of the words classified by the document sections ( Fig. 12 ) and through statistical graphs from the analysis of the textual corpus ( Figs. 13 and 14 ).

Decision making when choosing the tool
The entire systematic review process is extremely relevant for proposing a framework.And to facilitate decision-making when choosing one of the tools mentioned in this methodology, a decision flowchart was created according to the type of data obtained ( Fig. 15 ).

SODIP step 5: propose a conceptual and theoretical framework
The theory is the set of elements (e.g.concepts) that are interconnected and aim to explain and predict from the modelling of a framework [58] .The theory allows applying the key elements in practice, in addition to promoting questioning to generate more research and fill gaps contributing to the construction of theories [58] .There are two definitions to be considered when choosing between conceptual or theoretical framework proposals from the systematic review: a. Theoretical framework : it is the theoretical framework (a mother theory) chosen by researchers to guide the topic addressed, that is, it is epistemology, the explanation of the same theory to address a problem [58] .For example, common goods under the tragedy of commons theory [59] .b. Conceptual framework : it is the synthesis of several theories and different perspectives on the topic addressed [58] .For example, goods in common use from a perspective of the tragedy of the commons [59] and Socioecological Systems (SES) [60] .In other words, the conceptual framework is a deeper and more complex study than the theoretical framework, as it holistically uses various theories and perspectives.The purpose of both is to explain a question and propose ways to fill the gaps in the knowledge of the topic addressed (see examples in Table 13 ).The conceptual and theoretical frameworks can also be proposed following the PICO framework [61] ( Fig. 16 ).Here are some steps to formulate conceptual and theoretical frameworks [58] : 1. Synthesize concepts and perspectives through various sources: obtaining information from systematic review studies, metaanalysis, bibliometrics, scientific document databases, legislation documents and other data in open-access databases.
2. Understand the basic concepts to answer the guiding questions, hypotheses and objectives: identify trends and gaps by answering questions such as: What main topics are covered?What are the topics present or absent in the theory of the topic addressed?What is the spatial scale of the studies or data found?What is the time scale of the studies or data found?Why are studies missing in a period?3. Include transdisciplinary perspectives to answer a question: What needs to be improved theoretically or conceptually?4. Propose new ways to build the science of the topic addressed and fill gaps: What are the ways that this theory or concept should direct to new perspectives?Fig. 17 presents an overview of the proposed methodology.

Glossary
Bibliometry: The term bibliometrics was used for the first time in 1969 and has the advantage of studying geographic distribution, word frequency, and citations, among other relevant aspects of scientific documents [68] .Bibliometrics is a method that statistically measures the relationship of scientific documents [1 , 69] .The main indicators are i) quantity of measuring the productivity of the research group, ii) performance indicators of the quality of the journal, authors and other fields of research and iii) structural indicators of the connections between the previous themes [1 , 2] .Bibliometrics identifies theoretical trends in a topic addressed and explores future theoretical directions [70] , in addition to using big data to analyze these trends and identify gaps in knowledge.In addition, bibliometric studies need data encoded in databases [15] .Database: the systematized set of data (information) stored [71] (e.g.historical data stored in the Worldbank database).Databank: a large quantity of data on a particular topic [71] (e.g.historical data on SDG at the UN).
Data set: a collection of data [71] (e.g.Earth Observation Data the NASA).

Declaration of competing interest
None.The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Fig. 1 .
Fig. 1.Example to define the question and variables of interest for systematic review studies.Based on [4] .

Fig. 2 .
Fig. 2. Example of search words according to the spatial scale of the review studies.

Fig. 4 .
Fig. 4. Example of the spatial scale on SDG studies related to mangrove ecosystem [4] .

Table 3
PSALSAR Framework of the systematic review studies.

Table 5
Important dates for the mangrove ecosystem and socio-environmental research.

Table 6
Examples of coding search words.

Table 7
Boolean Operator Search Samples.

Table 8
Examples of review studies.

Table 9
Open access databases.